Panels can now be made with more abundant, less-expensive materials.

New research out of Berkeley Lab and the University of California suggests that it is possible to make solar cells from any semiconductor, opening the door to solar panels made from cheaper, more abundant materials.

Until now, phosphides and sulfides of metals have been judged ill-suited for solar cells because of the near-impossibility of chemically doping them with the quality of p-n junctions required. The new approach, dubbed "screening-engineered field-effect photovoltaics" (SFPV), sidesteps the problem by inducing p-n junctions in semiconductors by applying an electric field.

The p-n junctions in a solar cell are the borders between regions of semiconductor with a surplus of charge carriers and those with a shortfall. In a regular solar cell, these positive and negative regions are created by doping the base semiconductor, silicon, with phosphorus and boron, the atoms of which have a surplus and deficit of valence electrons in their outer shells compared to silicon. The p-n junction is crucial to the flow of useful electric current when the cell is exposed to light.

The problem is that the doping process necessitates relatively expensive materials. "Solar technologies today face a cost-to-efficiency trade-off that has slowed widespread implementation," said Alex Zettl, whose Zettl Research Group at UC Berkeley and the Lawrence Berkeley National Laboratory produced the paper Screening-engineered Field-effect Solar Cells. Though the crucial dollar-per-watt metric for photovoltaics is increasingly competitive, the authors argue that its "cost-to-efficiency trade-off" is still a barrier to widespread adoption.

Generally, more readily available semiconductors cannot be chemically doped either because the dopant materials diffuse through the material causing p-n junctions to break down, or because the doping process degrades the semiconductor itself, which can unacceptably compromise the solar cell's efficiency.

Instead, SFPV solar cells exploit the electric field effect. Concentrations of charge carriers within the semiconductor are manipulated by exposure to an electric field. Sustaining the field requires minuscule amounts of energy to maintain compared to the energy generated by the cell when exposed to sunlight.

This principle isn't new, but the key breakthrough is the precise geometry of the top electrode, which gets around the problem of screening and allows p-n junctions to form. Ordinarily, charge carriers in the metal contact move to cancel out the electric field in the nearby region of semiconductor, effectively creating a screen preventing the contact from further affecting charge carriers in the semiconductor.

"The trick behind our new approach is to geometrically structure the top contact in a special way such that the applied electric field doesn't get completely screened out by the top contact and can 'dope' the semiconductor below the contact to create a continuous p-n junction over the whole cell area," lead author Will Regan of the Zettl Group at UC Berkeley told Ars. And in fact the researchers have identified two ways of achieving this.

Courtesy Zettl Research Group, Lawrence Berkeley National Laboratory and University of California at Berkeley.

"The first way (type A) is to make the top contact very narrow, such that the applied electric field can sort of bleed around the contact," Regan explains. "The second way (type B) is to make the top contact very thin (e.g. a one-atom-thick sheet of graphene), so that the applied electric field can effectively penetrate through the top contact."

The research team claims that the approach will allow solar cells to be made "from virtually any semiconductor," and they have backed up their theory with working prototypes based on copper oxide and, ironically, silicon.

What's next for the project? "This research opens up scores of new semiconductors (many metal oxides, sulfides, and phosphides) for practical photovoltaic applications, so we are currently identifying the ones with the greatest potential for low-cost, high-efficiency solar cells," Regan told Ars. "For the best materials, we'll perform simulations to inform cell design and make experimental prototypes. We're also figuring out how much we can cost-effectively boost efficiencies for current industrial materials."

If there's a barrier to market entry it's that new manufacturing processes will be required to produce SFPV solar cells at a commercial scale. "There are several methods out there for making industry-scale nanostructured electrodes which are rapidly gaining traction," Regan said. "So we think that adoption by existing manufacturers could happen relatively soon."

Promoted Comments

I confess I didn't understand the article at all, but it seems excellent news. I look forwards to seeing cheap as chips solar panels plastered over everything. What with ultra-low voltage LEDs that already stay on for several second *after* unplugging from mains electricity, lighting looks on its way to being a solved problem.

Metal oxides, among other materials, have the potential to be great, cheap solar panels. Unfortunately, the microscopic components that comprise solar cells have a tendency to break down over time. These guys just discovered that you can prevent that breakdown by maintaining an electric field throughout the panel. This electric field uses less power than the solar panel generates, so you have a net surplus of energy. Thus we should be able to make them from a wider variety of materials than just silicon, allowing us to make cheaper panels, or more efficient panels, or ones that are both.

56 posts | registered Mar 19, 2012

James Holloway
James is a contributing science writer. He's a graduate of the Open University, with a B.Sc. in Technology and a Diploma in Design and Innovation. Twitter@jamesholloway

85 Reader Comments

I confess I didn't understand the article at all, but it seems excellent news. I look forwards to seeing cheap as chips solar panels plastered over everything. What with ultra-low voltage LEDs that already stay on for several second *after* unplugging from mains electricity, lighting looks on its way to being a solved problem.

I confess I didn't understand the article at all, but it seems excellent news. I look forwards to seeing cheap as chips solar panels plastered over everything. What with ultra-low voltage LEDs that already stay on for several second *after* unplugging from mains electricity, lighting looks on its way to being a solved problem.

Metal oxides, among other materials, have the potential to be great, cheap solar panels. Unfortunately, the microscopic components that comprise solar cells have a tendency to break down over time. These guys just discovered that you can prevent that breakdown by maintaining an electric field throughout the panel. This electric field uses less power than the solar panel generates, so you have a net surplus of energy. Thus we should be able to make them from a wider variety of materials than just silicon, allowing us to make cheaper panels, or more efficient panels, or ones that are both.

In terms of material costs, the glas substrate dominates everything. Even Indium does not contribute substatially to costs.

And even if the cell would costs exactly nothing, the total cost of an entire photovoltaic installation is dominated by framing, installation and power/control electronics costs. Seriously guys ... neat research, but solar power has reached a dead end.

I confess I didn't understand the article at all, but it seems excellent news. I look forwards to seeing cheap as chips solar panels plastered over everything. What with ultra-low voltage LEDs that already stay on for several second *after* unplugging from mains electricity, lighting looks on its way to being a solved problem.

Metal oxides, among other materials, have the potential to be great, cheap solar panels. Unfortunately, the microscopic components that comprise solar cells have a tendency to break down over time. These guys just discovered that you can prevent that breakdown by maintaining an electric field throughout the panel. This electric field uses less power than the solar panel generates, so you have a net surplus of energy. Thus we should be able to make them from a wider variety of materials than just silicon, allowing us to make cheaper panels, or more efficient panels, or ones that are both.

Not to nerd-bomb what looks like an exciting new approach, but wouldn't this have implications for long-term storage of the solar-panel material in the absence of an electric field?

In terms of material costs, the glas substrate dominates everything. Even Indium does not contribute substatially to costs.

And even if the cell would costs exactly nothing, the total cost of an entire photovoltaic installation is dominated by framing, installation and power/control electronics costs. Seriously guys ... neat research, but solar power has reached a dead end.

You are going to *eat* those words in 10 years. There's way more going on in solar than thin-film,

I confess I didn't understand the article at all, but it seems excellent news. I look forwards to seeing cheap as chips solar panels plastered over everything. What with ultra-low voltage LEDs that already stay on for several second *after* unplugging from mains electricity, lighting looks on its way to being a solved problem.

Metal oxides, among other materials, have the potential to be great, cheap solar panels. Unfortunately, the microscopic components that comprise solar cells have a tendency to break down over time. These guys just discovered that you can prevent that breakdown by maintaining an electric field throughout the panel. This electric field uses less power than the solar panel generates, so you have a net surplus of energy. Thus we should be able to make them from a wider variety of materials than just silicon, allowing us to make cheaper panels, or more efficient panels, or ones that are both.

Not to nerd-bomb what looks like an exciting new approach, but wouldn't this have implications for long-term storage of the solar-panel material in the absence of an electric field?

Good question! What effect would a year of being in a box in a warehouse before delivery have? I wonder how small the necessary current is - perhaps a small battery attached at manufacture-time would preserve it long enough.

In terms of material costs, the glas substrate dominates everything. Even Indium does not contribute substatially to costs.

And even if the cell would costs exactly nothing, the total cost of an entire photovoltaic installation is dominated by framing, installation and power/control electronics costs. Seriously guys ... neat research, but solar power has reached a dead end.

Until the price comes down to where the norm is people installing roofing of solar panels rather than traditional tiles, and that the power can be used to replace non-renewable fuels, not enough has been done. And then there still is the issue of the low efficency of solar panels ~20%, which could also use a huge improvement.

Some quantification in the article would be nice.... Exactly how much cheaper do they expect to make solar cells (per watt)? To be honest, it sounds like very early research in the area, and we shouldn't expect anything for a while.

In terms of material costs, the glas substrate dominates everything. Even Indium does not contribute substatially to costs.

And even if the cell would costs exactly nothing, the total cost of an entire photovoltaic installation is dominated by framing, installation and power/control electronics costs. Seriously guys ... neat research, but solar power has reached a dead end.

We should just give up then. The tech isn't there right now, and according to dio82, it's something we'll never see, much like a rainbow in the dark.

In terms of material costs, the glas substrate dominates everything. Even Indium does not contribute substatially to costs.

And even if the cell would costs exactly nothing, the total cost of an entire photovoltaic installation is dominated by framing, installation and power/control electronics costs. Seriously guys ... neat research, but solar power has reached a dead end.

But you can still make cells more efficient, which brings down the framing, installation and power/control electronics costs per watt. One way to make cells more efficient is to find a structure that can use a wider array of materials, then experiment using many more material options than exist today.

I confess I didn't understand the article at all, but it seems excellent news. I look forwards to seeing cheap as chips solar panels plastered over everything. What with ultra-low voltage LEDs that already stay on for several second *after* unplugging from mains electricity, lighting looks on its way to being a solved problem.

Metal oxides, among other materials, have the potential to be great, cheap solar panels. Unfortunately, the microscopic components that comprise solar cells have a tendency to break down over time. These guys just discovered that you can prevent that breakdown by maintaining an electric field throughout the panel. This electric field uses less power than the solar panel generates, so you have a net surplus of energy. Thus we should be able to make them from a wider variety of materials than just silicon, allowing us to make cheaper panels, or more efficient panels, or ones that are both.

Not to nerd-bomb what looks like an exciting new approach, but wouldn't this have implications for long-term storage of the solar-panel material in the absence of an electric field?

Good question! What effect would a year of being in a box in a warehouse before delivery have? I wonder how small the necessary current is - perhaps a small battery attached at manufacture-time would preserve it long enough.

My thought would be you just don't bother to apply the electric field while the cell is in storage. You won't generate energy, but you don't cost energy either. Once it's set up, you hook up the input leads, and they start generating.

Might even make them easier/safer to install: You can hook them all up without any worry about electrical currents until you are done.

I confess I didn't understand the article at all, but it seems excellent news. I look forwards to seeing cheap as chips solar panels plastered over everything. What with ultra-low voltage LEDs that already stay on for several second *after* unplugging from mains electricity, lighting looks on its way to being a solved problem.

Metal oxides, among other materials, have the potential to be great, cheap solar panels. Unfortunately, the microscopic components that comprise solar cells have a tendency to break down over time. These guys just discovered that you can prevent that breakdown by maintaining an electric field throughout the panel. This electric field uses less power than the solar panel generates, so you have a net surplus of energy. Thus we should be able to make them from a wider variety of materials than just silicon, allowing us to make cheaper panels, or more efficient panels, or ones that are both.

Not to nerd-bomb what looks like an exciting new approach, but wouldn't this have implications for long-term storage of the solar-panel material in the absence of an electric field?

Good question! What effect would a year of being in a box in a warehouse before delivery have? I wonder how small the necessary current is - perhaps a small battery attached at manufacture-time would preserve it long enough.

My thought would be you just don't bother to apply the electric field while the cell is in storage. You won't generate energy, but you don't cost energy either. Once it's set up, you hook up the input leads, and they start generating.

Might even make them easier/safer to install: You can hook them all up without any worry about electrical currents until you are done.

I am unsure how this addresses the concern, that the material breaks down over time. Unless I am misunderstanding, and the degradation only occurs during exposure to sunlight.

In terms of material costs, the glas substrate dominates everything. Even Indium does not contribute substatially to costs.

And even if the cell would costs exactly nothing, the total cost of an entire photovoltaic installation is dominated by framing, installation and power/control electronics costs. Seriously guys ... neat research, but solar power has reached a dead end.

Until the price comes down to where the norm is people installing roofing of solar panels rather than traditional tiles, and that the power can be used to replace non-renewable fuels, not enough has been done. And then there still is the issue of the low efficency of solar panels ~20%, which could also use a huge improvement.

Solar panels are much more efficient when installed on the ground ( heat reduces their ability to generate electricity).

If more DC powered appliances make it to the market, it would negate the need for inverters.

A few points to make from the discussion so far:1 - Cost of installation - framing etc is not a major portion of cost for solar. The panels are. (Installation is typically 10 - 20% of the total cost. The framing goes from 10 - 15%. In some cases the framing is built into the cell.)2 - This is very early days on the research. Stay tuned.3 - The cost of the creation of solar cells is pressured by both the manufacturing process and the cost of materials. Both of which appear to be lowered by this new technology.4 - Solar won't be dead until the sun dies - if that happens solar panels will be the least of our worries.... }B*)

Until the price comes down to where the norm is people installing roofing of solar panels rather than traditional tiles.

Or even walls. If iron oxides can work, solar wall siding might be possible for sun facing walls.

Solar roofing has been available for years now but effective deployment is limited to regions where hail is non-existent. Sun facing wall solutions avoid the worst of the hail problems and could make solar viable to large swaths of the midwest. Traditional black panel cells are a non-starter for whole-wall installation but earth tone ones become a little more... marketable.

I am unsure how this addresses the concern, that the material breaks down over time. Unless I am misunderstanding, and the degradation only occurs during exposure to sunlight.

That's the way I understood the article as well. The cells require the current as a sort of maintenance to keep the P and N junctions from breaking down

The oxide based semiconductors disintegrate over time when they are operated in the sun without a bias voltage. If you keep them in the dark, unconnected, they're fine. (Think Cadium Sulfide) What the article was saying that if there is a bias voltage applied evenly over the entire surface, it provides a "virtual" dopant that makes a semiconductor out of the side with the oxide. The pair then become a solar cell. You could use a small array of solar cells or a battery to provide the bias voltage.

To the grump dio82: There are a lot of places in this world where there is no electrical service and no possibilities for service yet there are people living there. Solar might be the only option for power for those people. Current pricing for installs is about $4/Watt (that includes all the frames, inverters, labor etc.). I agree that the solar cell panels are the cheapest part of the install in a lot of cases. For out-in-the-boonies installs, the homeowner is likely to be the installer as well.

One thing I've noticed over the last year has been the huge increase in houses with solar panels in the South of England. Look out the window of the train on my daily commute through the Arun Valley and there are tonnes of them now.

I think when my other half and I switch from rent to mortgage we'll put panels on the whole roof. Hopefully the price will be lower then too!

In terms of material costs, the glas substrate dominates everything. Even Indium does not contribute substatially to costs.

And even if the cell would costs exactly nothing, the total cost of an entire photovoltaic installation is dominated by framing, installation and power/control electronics costs. Seriously guys ... neat research, but solar power has reached a dead end.

You are going to *eat* those words in 10 years. There's way more going on in solar than thin-film,

Oh yeah? I am following solar power closely, and for the past 5 years I have already said that all name-worthy breakthroughs have been made for PV. The end of any rapid gains in technology have been reached.

And I was right.

There is no fundamental difference between PV technologies five years ago and today. And there is no hope that any of the current technologies being investigated will make any significant dent into costs in the near future. The only thing that changed is that subsidiesed Chinese manufacturers are flooding the market with their production over-capacity of 10+ year old PV technologies(!).

Solar cannot phyisically compete with classical forms of energy production due to its diffuse and intermittent nature. And there is nothing in the world that can change that. In order to harvest any appreciable amount of solar energy you need to seal enormous amounts of land. The material expenditure, even for thin-film, is enormous and dwarfs any other production mode of energy.

By the way, grid parity is a very stupid argument for solar power. As long as there is no battery back-up system priced into those generatring costs, solar will always need to compete against 4-5 c/kWh grid electricity, and loose very badly.

Solar is neat for chopping off the day peak in electricity prices, that's about 2-3% of total electricity generation, but nothing more.

Perhaps one day, in a very distant future, the cheaper alternatives to solar power will be exhausted. But until that day, there is very little reason to waste money on solar outside of niches.

Edit:Re-reading my post, I sound very negative.

My (expert) opinion: Solar power cannot compete gainst grid electricity. And there is no golden bullet in sight to change that. Perhaps decades of hard percipitation by engineers with incremental baby-steps will change that, but who know how other technolgies will improve over that time?! Unlike "cheap PV", cheap and abundant shale gas has changed everything. Who is to say that there won't be any progress here in the future?

Despite this, niche off-grid solutions are awesome for solar power. Solar power is also great for shaving off the day peak in electricity prices.

Looking at roof prices, I also have a feeling that the incremental cost increase of getting rid of roof tiling and installing PV instead is not that big. That is a neat thing. I will follow that very closely and possibly install something like that onto the rooftop of my dream house in 2-3 years ...

@dio82I think you are right only in so much as your perspective is too limited to see the usefulness of PV. Most renewables are supplemental energy sources, while we would likely still require a backbone such as nuclear. Our energy grid should support a wide variety of sources, and should use alternative energy sources where they make the most sense. If the effectiveness of alternative sources increases, our reliance on fossil fuels will decrease and will create a sustainable future.

What we need are floating solar cell covered balloons with long drop cords to plug into our houses. That and large barges covered in solar cells floating in nearby oceans (for those with nearby oceans). Heck you could even connect the barges with the power generating devices that make use of wave energy. Wouldn't replace coal electricity, but it would supplement it. And every bit of supplementation we can make means we can burn less coal.

And every bit of supplementation we can make means we can burn less coal.

Coal is dead. Natural gas has killed it. There are no new coal plants planned in America, and many older ones are being scrapped in favor of gas. Gas has probably killed the nuclear renaissance as well. We'll have to see what the current crop of almost-prefab reactors do in terms of installation cost. If we can get nukes built under budget, they might still have a place in the next 30 years.